  function grayOut(vis, options) {
      // Pass true to gray out screen, false to ungray
      // options are optional.  This is a JSON object with the following (optional) properties
      // opacity:0-100         // Lower number = less grayout higher = more of a blackout
      // zindex: #             // HTML elements with a higher zindex appear on top of the gray out
      // bgcolor: (#xxxxxx)    // Standard RGB Hex color code
      // grayOut(true, {'zindex':'50', 'bgcolor':'#0000FF', 'opacity':'70'});
      // Because options is JSON opacity/zindex/bgcolor are all optional and can appear
      // in any order.  Pass only the properties you need to set.
      var options = options || {};
      var zindex = options.zindex || 50;
      var opacity = options.opacity || 70;
      var opaque = (opacity / 100);
      var bgcolor = options.bgcolor || '#000000';
      var dark=document.getElementById('darkenScreenObject');
      if (!dark) {
        // The dark layer doesn't exist, it's never been created.  So we'll
        // create it here and apply some basic styles.
        // If you are getting errors in IE see: http://support.microsoft.com/default.aspx/kb/927917
        var tbody = document.getElementsByTagName("body")[0];
        var tnode = document.createElement('div');           // Create the layer.
            tnode.style.position='absolute';                 // Position absolutely
            tnode.style.top='0px';                           // In the top
            tnode.style.left='0px';                          // Left corner of the page
            tnode.style.overflow='hidden';                   // Try to avoid making scroll bars
            tnode.style.display='none';                      // Start out Hidden
            tnode.id='darkenScreenObject';                   // Name it so we can find it later
        tbody.appendChild(tnode);                            // Add it to the web page
        dark=document.getElementById('darkenScreenObject');  // Get the object.
      }
      if (vis) {
        // Calculate the page width and height
/* Tom: removed as behaviour incorrect with FF 3.5 */
        if( document.body && ( document.body.scrollWidth || document.body.scrollHeight ) ) {
            var pageWidth = document.body.scrollWidth+'px';
            var pageHeight = document.body.scrollHeight+'px';
        } else  if( document.body.offsetWidth ) {
          var pageWidth = document.body.offsetWidth+'px';
          var pageHeight = document.body.offsetHeight+'px';
        } else
/* */          {
           var pageWidth='100%';
           var pageHeight='100%';
        }
        //set the shader to cover the entire page and make it visible.
        dark.style.opacity=opaque;
        dark.style.MozOpacity=opaque;
        dark.style.filter='alpha(opacity='+opacity+')';
        dark.style.zIndex=zindex;
        dark.style.backgroundColor=bgcolor;
        dark.style.width= pageWidth;
        dark.style.height= pageHeight;
        dark.style.display='block';
      } else {
         dark.style.display='none';
      }
}